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[54.240.197.233]) by smtp.gmail.com with ESMTPSA id r4-20020a05600c35c400b00389f368cf1esm975314wmq.40.2022.03.16.11.39.10 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 16 Mar 2022 11:39:11 -0700 (PDT) X-Outflank-Mailman: Message body and most headers restored to incoming version X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 5fc02b8e-a558-11ec-8eba-a37418f5ba1a DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=7hTe8lqUiQDtRa2eY7/ZeO/Y25PyQNsO2Qnt46oLy3Y=; b=mT46jWmHmz9VfTAbZ416/td5UINURUvs0TJNEqPRoQSTpuK1eb6zWj7jxSuqZzMY5v e9k8lRE3JzCQlcBNGdkTDGuj/mmMWE+LeVROAHMOukcVxnOBXCzNTOkZpQzW+Q12AFXF /22r4hGVAplRoLHn3lBEpDeBarOzO2aQ/KXfsVs0tMPjaZ0Kru45y8umicU4W6P2Nyf8 17zHSy9TB1a0e6FVvegDtDQKI8/lC1mdfV6eoxSWo3c8tlk9prUWcWv3knoTbIW3iQNs n4L/GqSzooqwWgB5ldLzq1tlKprSgYppJc8wHM3BzdFrAtLXih6Hz968phrtLCq8kFWA aVdw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=7hTe8lqUiQDtRa2eY7/ZeO/Y25PyQNsO2Qnt46oLy3Y=; b=NWDzpKSee+vBNmyamMpAujdRsu2B95FzpdxZ1RCvS25vQBPNzSANKUkxU3Y4wuD2ii oxMqRsOlHNmyUFnt7uCVcUKkiE13WNG8VMd+Q//yiIYQur6jWwAy27Rp9p972sBdLI2d MKa+dAO0tnGhscrpr/oyxUVxPPNTbnvvMvP1BbLZsG0vg9xUIjEYTLEgUpbeOUifK2b/ x39MVbnnJLdncKFFN2tW/7B2B4s/WDwtjos8hDQXqlfz6EkM4VlxAi65gv34l1UqsyEK tCcViFp1wSX115IN0nZsr0dnTlMm91/BmPYniJsleE6MPDGKq5cka6aY2XsMyQaS+RKy x5cg== X-Gm-Message-State: AOAM5337lyf+EOqmu20iarJV8KQPChHtYI9a8fu6Z28qMytMPFHikshg lfrWZaKbeHYyj/NtJ2045Iw1VoZlBIqBpzvv X-Google-Smtp-Source: ABdhPJwJSwDpjRLgkpBFdDwAmL+zFum5LxzHvz3UWLoG6C5yDmhDomO90pIDvRnzZ77YkTGlNCVX3g== X-Received: by 2002:a1c:7c06:0:b0:389:7fd0:f6ec with SMTP id x6-20020a1c7c06000000b003897fd0f6ecmr8318170wmc.44.1647455951712; Wed, 16 Mar 2022 11:39:11 -0700 (PDT) From: Raphael Ning To: xen-devel@lists.xenproject.org Cc: Raphael Ning , Raphael Ning , Andrew Cooper , George Dunlap , Jan Beulich , Julien Grall , Stefano Stabellini , Wei Liu , David Vrabel Subject: [XEN PATCH] evtchn/fifo: Don't set PENDING bit if guest misbehaves Date: Wed, 16 Mar 2022 18:38:41 +0000 Message-Id: <6b84a20b2753130cc62406a0fd14d2708f6f504b.1647455219.git.raphning@amazon.com> X-Mailer: git-send-email 2.32.0 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @gmail.com) X-ZM-MESSAGEID: 1647455980978100001 Content-Type: text/plain; charset="utf-8" From: Raphael Ning Currently, evtchn_fifo_set_pending() will mark the event as PENDING even if it fails to lock the FIFO event queue(s), or if the guest has not initialized the FIFO control block for the target vCPU. A well-behaved guest should never trigger either of these cases. There is no good reason to set the PENDING bit (the guest should not depend on this behaviour anyway) or check for pollers in such corner cases, so skip that. In fact, both the comment above the for loop and the commit message for 41a822c39263 xen/events: rework fifo queue locking suggest that the bit should be set after the FIFO queue(s) are locked. Take the opportunity to rename the was_pending variable (flipping its sense) and switch to the standard bool type. Suggested-by: David Vrabel Signed-off-by: Raphael Ning Reviewed-by: David Vrabel Tested-by: Luca Fancellu --- xen/common/event_fifo.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c index ed4d3beb10f3..6c74ccebebb7 100644 --- a/xen/common/event_fifo.c +++ b/xen/common/event_fifo.c @@ -165,7 +165,7 @@ static void cf_check evtchn_fifo_set_pending( unsigned int port; event_word_t *word; unsigned long flags; - bool_t was_pending; + bool_t check_pollers =3D false; struct evtchn_fifo_queue *q, *old_q; unsigned int try; bool linked =3D true; @@ -226,8 +226,6 @@ static void cf_check evtchn_fifo_set_pending( spin_unlock_irqrestore(&q->lock, flags); } =20 - was_pending =3D guest_test_and_set_bit(d, EVTCHN_FIFO_PENDING, word); - /* If we didn't get the lock bail out. */ if ( try =3D=3D 3 ) { @@ -249,6 +247,8 @@ static void cf_check evtchn_fifo_set_pending( goto unlock; } =20 + check_pollers =3D !guest_test_and_set_bit(d, EVTCHN_FIFO_PENDING, word= ); + /* * Link the event if it unmasked and not already linked. */ @@ -314,7 +314,7 @@ static void cf_check evtchn_fifo_set_pending( &v->evtchn_fifo->control_block->ready) ) vcpu_mark_events_pending(v); =20 - if ( !was_pending ) + if ( check_pollers ) evtchn_check_pollers(d, port); } =20 --=20 2.32.0